Rock drill



Nov, 2@, 1951 J DlTsQN 2,575,619

ROCK DRILL Filed Nov. 19, 1945 E .INVENTOR A rlillDitsom W HIS ATTORNEY.

Patented Nov. 20, 1 951 ROCK DRILL J. D. Ditson, Phillipsburg, N. J assignor to Ingersoll-Ra'nd Company, New York, N. Y., a corporation of New Jersey Application November 19, 1945, Serial No. 629,588

4 Claims.

This invention relates to rock drills, and more particularly to fluid actuated rock drills of the reciprocatory piston type.

One object of the invention is to prevent the entrance of dust along the working implement and its guide into the rock drill.

A more specific object is to direct air ejected from the piston chamber by the piston into the forward portion of the rock drill to preclude the passage of dust and dirt along the cooperating surfaces of the working implement and its guide into the rock drill.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawings accompanying this specification and in which similar reference numerals refer to similar parts,

Figure 1 is an elevation, partly in section, of a rock drill constructed in accordance with the practice of the invention and showing the piston and the valve controlling it in one of their limiting positions, and

Figure 2 is a view similar to Figure 1 showing the piston and the valve in other limiting positions.

Referring more particularly to the drawings, 20 designates, in general, a rock drill of the type commonly known as a paving breaker comprising a cylinder 2| having a piston chamber 22 and a free exhaust port 23 for the piston chamber.

The front end of the cylinder has a hollow extension 24 that seats in the end of a front head 25 to centralize these casing parts with respect to each other, and the internal surface 26 of the extension 24 serves as a guide for the stem 21 of a hammer piston 28 in the piston chamber 22.

The stem 2'! extends into a cavity 29 located in the rearward portion of the front head 25, and in the opposite end of the front head is a bore 30 to receive a working implement 3| the shank 32 of which extends into the cavity 29 to receive the blows of the piston 28. The bore 30 is sufficiently larger than the shank 32 to provide the clearance necessary for free sliding movement of the working implement in the front head.

In the form of rock drill illustrated, pressure fluid is utilized only in the rearward end of the piston chamber for driving the piston 28 forwardly on its working stroke and the piston is returned by air compressed by it in the front end of the piston chamber which communicates, through a series of ports 33, with volume chambers 34 in the wall of the cylinder 2i. The return of the piston is facilitated by utilizing the expansion of the compressed air, from the volume chambers 34, to aid the rebound of the piston 28 from the shank 32 thus imparting suflicient velocity to the piston so that the momentum of the piston will enable the completion of the return stroke. In order that compression of only a low pressure value may be required to thus return the piston, provision is made to permit the free expulsion of air from the rearward end of the piston chamber so that the piston may execute its return stroke with a minimum of resistance to its movement. The flow of such fluid from the piston chamber is controlled by the valve mechanism 35 which also controls the flow' of pressure fluid into the piston chamber. However, as will be readily understood, separate valves may be provided to perform these functions.

The valve mechanism 35 is arranged in a back head 36 forming a closure for the rearward end of the piston chamber. It comprises a valve chest 31 that lies in a bore 38 in the back head and serves as a seat for the hub portion 39 of a handle 40 whereby the rock drill may be held and guided with respect to the work.' The hub portion 39 constitutes the rearmost casing part of the rock drill and may be secured thereto in any suitable and Well known manner.

The valve chest 31 consists of three members 4|, 42 and 43 which are recessed to define a valve chamber 44 for the accommodation of a valve 45 of the sleeve type having an external flange 46 the rearmost surface of which constitutes an actuating surface 47 that is subjected to pressure fluid for throwing the valve forwardly, and on the skirt portion of the valve lying forwardly of the flange 46 is an opposed annular actuating surface 48 of smaller area than the surface 41 and is constantly exposed to pressure fluid at full line pressure for unseating the valve to admit pressure fluid into the piston chamber 22. Such pressure fluid is delivered into the front end of the valve chamber by a supply conduit 49 and passes into the piston chamber through an inlet opening 5 in the back head 36.

The front end 5| of the valve 45 is of reduced diameter to extend slidably into the inlet opening 50, and immediately rearwardly of said end 5| is an annular seating surface 52 to engage a seat 53 on the back head for limiting movement of the valve in a forwardly direction. The rearward end of the valve constitutes an opposed seating surface 54 that cooperates with a seat 55 on the valve cage member 43 to limit movement of the valve in a rearwardly direction, and in said member 43 are ports 56 thatare arranged around the seat 55 to afford communication between the rearward end of the valve chamber 44 and a recess 51 in the hub 39.

Pressure fluid also fiows constantly from supply for action against the actuating surface 4! to throw the valve forwardly against the seat 53, and the period of efiectiveness of such pressure fluid in the cycle of operation is controlled by the piston 28. To this end the back head 36 is provided with a constant supply passage 58 of restricted flow area for conveying pressure fluid from the supply conduit 49 to a tripper passage 59 leading from the rearward end of the recess 60 containing the valve flange 46 to the piston chamber 22 wherewith it communicates through a port 6| located at a point forwardly of the exhaust port 23.

The port BI is so positioned that when the piston rests upon the working implement 3! it will overlie the port Bl.

The port 6!, moreover, lies in the same transverse plane as the lower extremity 62 of a slot 63 that extends forwardly through the wall of the piston chamber from the exhaust port 23 to permit the escape of air from the piston chamber in excess of that required for the compression serving to retract the piston 28. By reason of this arrangement, the slot 63 and the port 6| will be covered and uncovered simultaneously, and during the downward stroke of the piston only air at atmospheric pressure will exist in the front end of the piston chamber for compression by the piston. In instances of use where the rock drill is connected directly to the discharge end of the compressor, after the manner illustrated more particularly in United States Patent #2378302 to Fred M. Slater, and in which case it may be desirable that the entire discharge output of the compressor pass through the piston chamber, even when the compressor is operating at idling speed as when the rock drill is inactive, the rock drill is provided with a leak passage 54 that leads from the rearward end of the recess 65 to a bore, 65 in the back head 36 beneath the handle 40 and is open to the atmosphere.

The outlet end of the borev 65 is controlled by a valve 616, and a spring 61 in the bore 65 acts against the valve for unseating it. The valve 56 is actuated manually in the opposite direction Y and has a stem 68 slidable through a boss 69 on the hub 39 for engagement with a wing 10 forming an integral portion of a lever II connected pivotally to the handle by a pin '12.

As is well known, rock drills of the paving breaker type are unprovided with means for flushing the working surface to allay dust resulting from drilling. In consequence, the atmosphere becomes heavily laden with dust which finds its way into the rock drill and, by its abrading action, causes serious wear on the movable parts and their guiding surfaces. For example, dust passes along the surfaces of the bore 30 and the working implement into the cavity 29. Its movement in this direction is usually accelerated by the relative endwise shifting of the working implement and the front head and by the pumping action of the piston stem 21.

In order to obviate this objectionable occurrence, it is contemplated herein to utilize the air expelled from the rearward end of the piston chamber 22, by the piston 28, as a medium for preventing the entrance of abrasive matter into the rock drill. To this end a tube 13 is arranged axially through the valve and piston chamber to communicate at one end with the recess 51 and at its other end with the cavity 29. By reason of this arrangement, the air expelled from the piston chamber will pass through the valve and the ports 56, thence through the tube 13 into the cavity 29 and escape therefrom to the atmosphere through the bore 30 and a vent 14 at the front end of the cavity.

The forward portion of the tube 13 is guided only by the piston 28 and the rearward portion of said tube lies within a stem 15 which depends from the valve cage member 43 and extends, in the present instance, through the valve 45 and the inlet port 55, said stem being smaller than the inlet port and the interior of the valve to permit the free flow of fluid medium through the port and the valve.

The tube has a nice sliding fit in the stem I5 to minimize the chances of leakage of pressure fluid through the stem and is held firmly in the assembled position by a packing sleeve 15 encircling the rearward end of the tube and lying within a recess "E7 in the member 43. The sleeve i6 is compressed into tight gripping engagement with the tube and its inner end is forced into sealing engagement with the bottom of the recess H by a cup-shaped gland 18 that contains the packing member and is threaded into the recess 7 The operation of the device is as follows: Let it be assumed that the piston is at rest in the foremost limiting position illustrated in Figure 2 to uncover the exhaust port 23 and that the discharge output of the compressor, while idling, is passing through the rearward end of the piston chamber and the exhaust port 23 to the atmosphere, it'being understood that the pressure fluid flowing from the compressor will be acting against the actuating surface 48 and lift the valve to its rearmost limiting position. In its forward position, the piston will cover the tripper passage 59 and pressure fluid entering it from the port 58 will escape to the atmosphere through the recess 65, the passage 54 and the bore 65.

If, under these conditions, it be intended to set the hammer piston 28 in motion, the valve 66 is pressed against the back head 36 by the lever H to seal the bore 65. The pressure fluid thereafter flowing into the tripper passage will quickly reach line value and, acting against the actuating surface ll, will throw the valve forwardly to cut-off admission into the rearward end of the piston chamber. At the same time pressure fluid flows downwardly from the tripper passage 59 through the clearance existing between the piston and the wall of the piston chamber into the front end thereof, this being the clearance that is normally provided between the piston 28 and the wall of the piston chamber 22- to assure free running of the piston. When the required pressure is attained in the front end of the piston chamber the piston. will be moved rearwardly thereby until the front end of the piston uncovers the port 61 and the gash 63. The fluid in the rearward end of the recess 65 will then escape through the passage 55, the piston chamber 22 and the exhaust port 23 to the atmosphere. At the same time, the pressure fluid acting against the actuating surface 23. will move the valve rearwardly to communicate the inlet. opening with the front end of the valve chamber. Pressure fiuid will then flow from the front end of the valve chamber into the adjacent end of the inlet opening 50.

the piston chamber and drive the piston forwardly against the working implement.

During such charging of the piston chamber, pressure fluid also flows from supply through the constant supply passage 58 into the tripper passage 59, and when the piston reaches a position to cover the port 6! the pressure fluid thereafter leaking into the tripper passage will be en trapped therein and act against the surface ll and again throw the valve 45 forwardly to close This movement of the valve will take place immediately before the piston uncovers the exhaust port 23 so that no pressure fluid will flow from supply to the atmosphere without first doing useful work. During the remainder of the forward stroke of the piston, the air entrapped in the piston chamber forwardly of the gash 63 will be compressed by the piston and will augment the rebound of the piston from the working implement to return the piston.

During the time of valve 45 is in position to close the inlet opening 50 the interior of the valve will be in free communication with the ports 56. The air in the portion of the piston chamber lying rearwardly of the exhaust port 23 will then be expelled by the piston through the inlet opening 50, the interior of the valve and the ports 56 into the recess 51, whence it passes through the tube 13 into the cavity 29 and escapes therefrom through the port 14 to the atmosphere.

Some of the air thus delivered to the cavity 29 will also flow through the bore 30 to prevent the entrance of dust thereinto and the lodgement of dust around the outer end of the bore 30 and the adjacent surface of the working implement and, in this way, prevent the admission of dust to the important bearing surfaces of the costly parts of the rock drill.

The rock drill continues to operate in the manner described as long as the valve 66 seals the bore 65 and when it is intended to terminate an operating period of lever H is released. The spring 61 and the pressure fluid in the bore 65 will then lift the valve 66 and permit the pressure fluid flowing from the passage 58 into the tripper passage 59 to escape through the leak passage 64 and the bore 65 to the atmosphere to prevent the building up of pressure fluid against the surface 4! of the valve 45.

The pressure fluid acting against the surface 48 of the valve 45 will then shift said valve rearwardly against the seat 55 and will hold it thus as long as the bore 65 remains uncovered. The

pressure fluid thereafter flowing from supplythrough the valve chamber, the rearward end of the piston chamber and the exhaust port 23 to the atmosphere will retain the piston in its foremost limiting position against the working implement 31 as long as the valve 66 remains unseated.

I claim:

1. In a fluid actuated rock drill, a casing having a piston chamber and a cavity, a working implement extending into the cavity, a reciprocatory piston in the piston chamber for actuating the working implement, an outlet opening at the rear end of the piston chamber, valve means to control the outlet opening for controlling the escape of fluid displaced by the piston on its rearward stroke from the piston chamber, and means for conveying such fluid to the cavity for preventing the passage of dust from the atmosphere along the surface of the working implement toward the cavity.

2. In a fluid actuated rock drill, a casing having a piston chamber and a cavity, a working implement extending into the cavity, a reciprocatory piston in the piston chamber having a stem extending into the cavity for actuating the working implement, an outlet opening at the rear end of the piston chamber, valve means to control the outlet opening for controlling the flow of fluid displaced by the piston in the rearward end of the piston chamber, a pressure surface on the valve means, means for conveying pressure fluid to said pressure surface for actuating the valve means, and a conduit for conveying such displaced fluid to the cavity for preventing the passage of dust from the atmosphere along the surface of the working implement toward the cavity.

3. In a fluid actuated rock drill, a casing having a piston chamber and a cavity, a working implement extending into the cavity, a reciprocatory piston in the piston chamber to actuate the working implement, an outlet opening at the rear end of the piston chamber, valve means to control the outlet opening for controlling the flow of fluid displaced by the piston in one end of the piston chamber, a pressure surface on said means, a passage in the casing communicating the pressure surface with the chamber, a passage in the casing for conveying pressure fluid to the first said passage for actuating the valve means, and a conduit arranged axiall in the rock drill to convey fluid displaced by the piston to the cavity for preventing the passage of dust from the atmosphere along the working implement toward the cavity.

4. In a fluid actuated rock drill, a casing having a piston chamber and a cavity forwardly thereof, a working implement extending into the cavity, a reciprocatory piston in the piston chamber to actuate the working implement, a recess in the casing rearwardly of the piston chamber, an outlet opening at the rear end of the piston chamber leading to the recess, valve means to control the outlet opening for controlling the flow therethrough into the recess of fluid displaced and expelled from the piston chamber by the piston during its rearward movement, a conduit for conveying such fluid from the recess to the cavity, and an atmospheric vent in the easing for the cavity.

J. D. DITSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,080,095 Bayles Dec. 2, 1913 1,499,569 Bailly July 1, 1924 FOREIGN PATENTS Number Country Date 485,143 France Sept. 22, 1917 445,089 Great Britain Apr. 2, 1936 

